Published on February 17, 2025 by Global Triathlon Network, this video is essential viewing for triathletes and endurance athletes looking to improve their performance and deepen their understanding of the sport. Whether you're preparing for your first sprint triathlon or chasing a Kona qualification slot, the insights shared here are directly applicable to your journey. Here's our comprehensive companion guide with in-depth analysis, practical takeaways, and expert context to help you get the most from this content and apply it to your own training and racing.
Fueling Strategy Overview
Nutrition is the fourth discipline of triathlon, and this Global Triathlon Network video breaks down the science and practice of race fueling with expert insight. Key points: "Racing in the heat can be quite a task, especially when you are not acclimatised! But how much does the heat really affect your performance? James heads over to the Precision Fuel & Hydration......" Getting your nutrition right can be the difference between a personal best and a DNF — and unlike fitness gains that take months to develop, nutrition improvements can be implemented almost immediately.
The evolution of sports nutrition science over the past decade has been remarkable and has fundamentally changed how athletes at every level approach fueling. We now understand that trained athletes can absorb and utilize far more carbohydrate per hour than previously believed — up to 120g/hr using dual-transport carbohydrate formulations that leverage both glucose and fructose absorption pathways. This breakthrough has reshaped race-day nutrition strategies from the professional ranks down to age-group competition, enabling athletes to maintain higher power outputs and faster running paces deep into long-distance events.
Pre-Race Nutrition and Glycogen Loading
Carbohydrate loading in the 48-72 hours before race day is one of the most evidence-supported nutrition strategies in endurance sport. The goal is to maximize glycogen stores in your muscles and liver, providing readily available fuel for the enormous energy demands ahead. Research consistently shows that athletes who effectively carb-load perform 2-3% better in events lasting more than 90 minutes compared to those who don't — a significant margin that translates to several minutes in a triathlon.
A practical carb-loading approach: increase your carbohydrate intake to 8-10g per kilogram of bodyweight per day for 2-3 days before the race. For a 70kg athlete, that means consuming 560-700g of carbohydrate daily. Focus on easily digestible sources that won't cause GI discomfort: white rice, pasta, bread, energy bars, pancakes, and sports drinks. Reduce fiber and fat intake during this period to minimize digestive issues and make room for the increased carbohydrate volume. This isn't the time for salads and brown rice — go for simple, processed carbohydrates that your body can absorb efficiently.
Your race morning meal should be consumed 2.5-3 hours before the start to allow complete gastric emptying. Aim for 100-150g of carbohydrate from familiar, easily digestible foods that you've tested multiple times in training. Many athletes rely on oatmeal with honey, white toast with jam, or rice cakes with peanut butter. Avoid anything new — race morning is not the time for dietary experiments. A final 30g of easily digestible carbohydrate 5-10 minutes before the swim start can top off blood glucose levels without causing insulin rebound.
During-Race Fueling: Absorption Science and Practical Application
During exercise, your body can oxidize approximately 60g of glucose per hour through the SGLT1 intestinal transport pathway. By adding fructose, which uses the separate GLUT5 transporter, you can increase total carbohydrate oxidation to 90-120g per hour in well-trained guts. This dual-transport approach is the science behind modern sports nutrition products labeled "2:1" or "1:0.8" glucose-to-fructose ratios, and it represents one of the most significant practical advances in endurance sport nutrition.
For a 70.3 distance race, target 60-80g of carbohydrate per hour on the bike and 40-60g on the run. For full IRONMAN distance, maintain similar bike targets with 40-60g per hour on the marathon. Start fueling within the first 15-20 minutes of the bike leg to stay ahead of the energy curve — your glycogen stores are already partially depleted from the swim, and falling behind on nutrition creates a deficit that's almost impossible to recover from later in the race.
Practice your nutrition strategy in training before race day — this cannot be overemphasized. Your gut needs to be trained just like your muscles and cardiovascular system. The intestinal transporters that absorb carbohydrate become more efficient with regular training, meaning an athlete who practices race-day nutrition during training blocks can absorb and utilize significantly more fuel than one who only eats during races. Start with lower calorie targets and build up over 4-6 weeks, testing different products and timing to find what works specifically for your body.
GI distress on race day is almost always a training oversight, not bad luck. The most common causes are: trying a new product on race day, taking in too much at once rather than small amounts frequently, dehydration (which reduces gut blood flow and impairs absorption), and excessive fat or fiber intake in pre-race meals. By systematically testing your nutrition plan in training and eliminating these risk factors, you can race with confidence that your gut will cooperate.
Hydration Strategy and Electrolyte Balance
Dehydration impairs performance long before you feel thirsty. Research shows that a 2% loss of body weight through sweat reduces endurance performance by 10-20%, primarily through reduced blood volume, increased heart rate, and impaired thermoregulation. However, over-hydration — a condition called hyponatremia — is equally dangerous and can be life-threatening. The goal is to match fluid intake to sweat losses as closely as practical without overdoing it.
Sweat rates vary dramatically between individuals and conditions — from as little as 500ml to over 2.5 liters per hour depending on genetics, fitness level, heat acclimatization, and environmental conditions. A simple sweat test, performed by weighing yourself before and after a one-hour workout (accounting for fluid consumed), helps you determine your personal needs. During racing, aim to replace 75-80% of your sweat losses — complete replacement isn't necessary and can increase the risk of hyponatremia and GI distress.
Sodium is the critical electrolyte lost in sweat, with individual losses ranging from 200-1800mg per liter of sweat depending on genetics and acclimatization. Most commercial sports drinks contain 300-500mg of sodium per liter, which is adequate for average sweaters but insufficient for heavy or salty sweaters. If you notice white residue on your clothing after exercise, you're likely a salty sweater who needs supplemental sodium tablets. Racing in hot and humid conditions demands more aggressive electrolyte replacement than cool-weather events.
Develop a hydration plan that accounts for your specific race conditions. In hot races, you may need to consume 750-1000ml per hour and increase sodium intake significantly. In cooler conditions, 400-600ml per hour may suffice. Use the bike leg to dial in hydration and enter the run well-hydrated, as running makes it harder to consume large volumes of fluid without GI distress. Practice drinking at race effort during training to build tolerance.
Post-Race Recovery Nutrition
What you eat after training and racing matters almost as much as what you eat during. Post-exercise nutrition windows are physiologically real — your muscles are most receptive to glycogen replenishment and protein synthesis in the 30-60 minutes immediately following exercise. Consistency with recovery nutrition across weeks and months of training compounds into meaningful fitness gains through better adaptation and reduced injury risk.
The ideal recovery meal or shake contains 1-1.2g of carbohydrate per kilogram of bodyweight and 0.3-0.4g of protein per kilogram. For a 70kg athlete, that's 70-85g of carbohydrate and 20-28g of protein within 30 minutes of finishing. Practical options include chocolate milk (which hits these targets remarkably well), a protein smoothie with fruit and oats, or a meal of rice with chicken or fish. The combination of carbohydrate and protein is synergistic — together they stimulate faster glycogen replenishment than carbohydrate alone.
In the 24 hours following a major race or training session, focus on three priorities: rehydrating fully until your urine is pale yellow, replenishing glycogen stores with frequent carbohydrate-rich meals and snacks, and providing adequate protein for muscle repair and adaptation. Anti-inflammatory foods like berries, fatty fish, turmeric, and tart cherry juice can support the recovery process, though they should complement rather than replace a solid whole-food diet.
Evidence-Based Supplements for Endurance Athletes
The sports supplement industry generates billions of dollars annually, but only a handful of products have strong scientific support for endurance performance. The evidence-based supplements worth considering are: caffeine (3-6mg/kg for reducing perceived exertion and improving performance by 2-4%), creatine monohydrate (for power output and enhanced recovery), beta-alanine (for buffering acid in high-intensity efforts), and sodium bicarbonate (for similar buffering benefits in shorter events). Everything else is either marginal, unproven, or marketed based on weak evidence.
Caffeine deserves special attention for endurance athletes. Consumed 30-60 minutes before exercise at 3-6mg per kilogram of bodyweight, it reduces perceived exertion and improves endurance performance by an average of 2-4% across dozens of well-controlled studies. Many athletes also use caffeine strategically during the run leg of long-distance races when fatigue peaks — flat cola or caffeinated gels can provide a meaningful boost when your legs are screaming. Practice your caffeine strategy in training to calibrate dose, timing, and tolerance, as individual sensitivity varies widely.
Vitamin D, iron, and omega-3 fatty acids are worth monitoring through blood work rather than supplementing blindly. Many endurance athletes are deficient in one or more of these micronutrients due to high training volumes and dietary gaps. A sports-focused blood panel once or twice per year can identify deficiencies that may be limiting your performance and recovery — fix these through targeted supplementation or dietary changes rather than taking a multivitamin and hoping for the best.
Building Your Personal Nutrition System
No nutrition plan works universally — individual variation in gut tolerance, sweat rate, taste preference, and metabolic efficiency means you need to find YOUR formula through systematic experimentation. Keep a nutrition log during training to track what you consumed, when you consumed it, how you felt, and how you performed. Over weeks of data collection, clear patterns will emerge about what works and what doesn't for your unique physiology.
Start with evidence-based guidelines as your framework, then adjust based on personal experience and data. If 80g of carbs per hour causes GI distress, back off to 60g and build up gradually over several weeks. If you can't stomach gels, try real food alternatives like rice balls, energy chews, or blended fruit pouches. If one brand of sports drink sits well but another causes bloating, that information is pure gold. The best nutrition plan is the one you can actually execute consistently on race day without gastric rebellion.
Consider working with a sports dietitian who specializes in endurance sport, especially if you're preparing for a full-distance event. A personalized nutrition plan based on your body composition, sweat rate testing, training schedule, and race goals can remove the guesswork and accelerate your path to optimal fueling. Many athletes find that professional nutrition guidance yields bigger performance gains than any equipment upgrade.
Watch the Full Video
Hit play above to watch the complete nutrition guide from Global Triathlon Network. For more nutrition science and practical fueling strategies, explore our training guides, upcoming races, and athlete profiles on EnduranceFinder. Dial in your nutrition and unlock performance gains you didn't know you had.
